考虑波浪运动影响的边界层风场特性研究

海上风场由于受动态波浪下垫面影响,粗糙度随着波龄、波陡、波高等状态发生变化,其特性较陆地风场更为复杂。为研究波龄对风场特性的影响,建立了正弦运动下垫面、自由滑移顶面计算模型,采用大涡模拟的方法,选取9种不同波龄取值,对海上风场环境进行模拟,分别对不同波龄下的风剖面等平均风特性及脉动风剖面进行了研究。研究发现,波浪的运动对上层流场有着显著的影响,给出了不同波龄下的平均风速剖面,分析了它们随波龄的变化规律,并通过雷诺应力分量的剖面计算,分析了波龄对于风场湍流特性的影响。     

Direct detection of chicken genomic DNA for gender determination by thymine-DNA glycosylase

1. Birds, especially nestlings, are generally difficult to sex by morphology and early detection of chick gender in ovo in the hatchery would facilitate removal of unwanted chicks and diminish welfare objections regarding culling after hatch. 2. We describe a method to determine chicken gender without the need for PCR via use of Thymine-DNA Glycosylase (TDG). TDG restores thymine (T)/guanine (G) mismatches to cytosine (C)/G. We show here, that like DNA Polymerase, TDG can recognise, bind and function on a primer hybridised to chicken genomic DNA. 3. The primer contained a T to mismatch a G in a chicken genomic template and the T/G was cleaved with high fidelity by TDG. Thus, the chicken genomic DNA can be identified without PCR amplification via direct and linear detection. Sensitivity was increased using gender specific sequences from the chicken genome. 4. Currently, these are laboratory results, but we anticipate that further development will allow this method to be used in non-laboratory settings, where PCR cannot be employed.     

Direct and sensitive detection of Trypanosoma evansi by polymerase chain reaction.

The mechanically transmitted haemoflagellate, Trypanosoma evansi causes 'surra', a wasting disease of domestic animals and is highly endemic in distribution in Southeast Asia. The detection of T. evansi is important for improving the epizootiological and animal health status of the region. The specificity and sensitivity of polymerase chain reaction (PCR) using oligonucleotide primers constructed from T. evansi repetitive DNA sequences were studied in the present investigation. Using the assay, it was possible to amplify template DNA of T. evansi derived from buffaloes, camels and horses to a threshold sensitivity level of 0.5 pg and to detect DNA from as few as five organisms in 10 microliters crude blood samples. Following experimental infection of calves with 5 x 10(5) T. evansi, positive signals could be observed as early as 12 h post-infection. DNAs from two common haemoflagellates of cattle, Babesia bigemina and Theileria annulata were not amplified with the primers.     

Duplex Doppler Estimation of Intrarenal Pourcelot Resistive Index in Dogs and Cats With Renal Disease

In human beings, intrarenal blood flow impedance, expressed as the resistive index (Rl) and obtained by duplex Doppler ultrasonography, has been used to aid in diagnosis and prognosis of renal failure. Higher than normal values for Rl were obtained in 3 of 4 dogs with acute tubular necrosis (ATN) and in 5 of 10 dogs with glomerulonephrosis (GN). Normalization of Rl was observed in 2 dogs with ATN evaluated serially during treatment. Increased Rl values were obtained in 9 of 10 cats with nonobstructive renal disease and in 2 of 5 cats with obstructive renal disease. Normalization of Rl was observed in 3 cats with renal failure in which treatment was effective (1 with obstruction; 2 with nonobstructive disease). The magnitude of increase in Rl did not correlate with the magnitude of concurrent renal dysfunction. These results suggest that duplex Doppler evaluation of intrarenal Rl is more useful as an ancillary diagnostic technique in azotemic dogs with ATN than in those with GN and in azotemic cats with nonobstructive than in those with obstructive disease.     

Direct polymerase chain reaction detection of Campylobacter spp. in poultry hatchery samples

A rapid, sensitive, and specific polymerase chain reaction (PCR) assay was developed for the direct detection of Campylobacter in environmental samples from hatcheries. PCR, with a set of primers specific for the Campylobacter flaA short variable region (SVR), detected the presence of Campylobacter in both fluff and eggshell samples; however, a determination of whether the organism was living or dead could not be made. Conventional cultural methods detected no Campylobacter from the same samples. An additional benefit of the direct PCR assay is it allows for the production of a product that can be sequenced to provide further epidemiologic information.     

Direct detection of Actinobacillus (Haemophilus) pleuropneumoniae in the lungs of swine

By means of cultural examination, coagglutination test (CT) and indirect fluorescent-antibody-technique (IFAT) a total of 199 lung specimens from necropsy pigs from Northwestern Germany with symptoms of pleuropneumonia was examined for Actinobacillus (Haemophilus) pleuropneumoniae (AP). The CT was used to detect type specific antigens in lung extracts and the IFAT was performed on tissue sections. Both tests were found to be specific. Detection and identification of AP by either test were successful in 68 of 199 lung specimens. AP was isolated out of 40 lungs, antigen detection by CT was successful in 40 and by IFAT in 65 lung samples. In 26.5% of the positive samples AP was demonstrated only by IFAT. In 4.4% of the positive specimens AP was demonstrated only by cultural examination, but the detected serovars were not accounted in IFAT and CT. In 44.1% of the positive specimens AP was isolated or detected by all three techniques. The predominating serovar was serovar 9 followed by 2 and 7. One field isolate could be identified as serovar 3 and another one as serovar 10. Furthermore one isolate was untypable. IFAT and CT were limited for detection of serovars 2, 7 and 9. Detection of multiple serovars in few lung samples was successful only by IFAT. Indirect fluorescent-antibody-technique was found to be more sensitive than coagglutination test and cultural examination. On the other hand CT was found to be less time consuming and easier to evaluate than other tests. By this, coagglutination test seems to be preferable in examining large numbers of lung samples.     

Evaluation of Right Ventricular Myocardial Function in Healthy Horses With Recurrent Airway Obstruction Using Tissue Doppler Imaging

It has been described in humans that chronic obstructive bronchitis leads to pathologic changes, especially in the right ventricular myocardium due to hypoxia, which can be assessed by tissue Doppler imaging (TDI). In our study, different TDI techniques, that is, pulsed-wave TDI and color TDI, were evaluated for applicability in different scan planes (apical long-axis view and short-axis view) for the analysis of right ventricular myocardial function in six healthy horses (control) and six horses affected with recurrent airway obstruction (RAO) (RAO group). Tissue Doppler imaging was applicable to all scan planes described. Myocardial movement directions in general and the absolute values of TDI parameters were assessable. Significantly reduced early diastolic filling velocities (E), elevated late diastolic filling velocities (A), thereby decreased E/A quotient, prolonged electromechanical coupling periods between electrocardiograph Q-wave and maximal velocities, and compensatory elevated systolic strain as well as diminished displacement could be observed in horses with RAO compared with the control group. To conclude, equine right ventricular myocardial function is assessable by TDI. Significant changes of right ventricular myocardial function could be demonstrated by TDI in horses with RAO compared with matched healthy controls. The hypothesis that RAO potentially leads to right ventricular dysfunction detectable by TDI before conventional echocardiography changes are evident is supported by this explorative study.     

Direct immunofluorescence tests with counterstains for detection of Chlamydia psittaci in infected avian tissues.

Different methods of preparation and serological evaluation of rabbit globulins for use in fluorescent antibody conjugate and different methods of counterstaining with fluorescent antibody tests were evaluated for detection of Chlamydia psittaci in infected turkey tissues. The agar gel precipitin reaction was that chosen for testing and selecting antiserums to be used for fluorescein isothiocyanate conjugation. The fluorescent antibody staining was most pronounced with conjugate made from globulins precipitated with ammonium sulfate. A direct fluorescent antibody method with Evans blue counterstain correctly identified "coded" specimens of C. psittaci-infected and noninfected turkey air sacs. However, naphthalene black was superior to Evans blue as a counterstain when infected pericardial sacs were tested.     

Direct agglutination test for the detection of antibodies to Sarcocystis neurona in experimentally infected animals

Equine protozoal myeloencephalitis (EPM) is a serious neurological disease of horses in the Americas. The apicomplexan protozoan most commonly associated with EPM is Sarcocystis neurona. A direct agglutination test (SAT) was developed to detect antibodies to S. neurona in experimentally infected animals. Merozoites of the SN6 strain of S. neurona collected from cell culture were used as antigen and 2-mercaptoethanol was added to the antigen suspension to destroy IgM antibodies when mixed with test sera. Mice fed sporocysts of S. speeri or S. falcatula-like sporocysts from opossums did not seroconvert in the SAT. The sensitivity of the SAT was 100% and the specificity was 90% in mice.